Cadmium has long been used as an ingredient of glass, including fritted glass. One important use of cadmium fritted glass is as a stabilizer for inorganic red or yellow glazes, that is, to prevent such glazes from burning out and discoloring at elevated temperatures. For example, cadmium sulfide yellow and cadmium sulfoselenide red are two pigments that can be mixed with low melting base frit or glasses, applied to ceramic or glass bodies, and then fired to provide colored glazes ranging from brilliant yellow through orange and red to maroon.
To provide temperature stable yellow to red glazes containing cadmium sulfide and/or cadmium sulfoselenide as a color carrier, it has been the practice to form a base frit and a color frit in which the color frit contains the cadmium, sulfur, and/or selenium compounds. U.S. Pat. Nos. 3,527,649 to Sullivan and No. 4,008,091 to Wagner et al relate to processes for producing cadmium-containing glazes.
In the course of producing cadmium glazes, and in the actual use of cadmium bearing glasses, many workers necessarily must handle the glasses or otherwise become exposed to them.
There is a growing concern about possible cadmium poisoning due to ingested material or inhaled dust of a cadmium-containing glass, especially in finely divided frit form, or due to direct contact with a cadmium-containing glass. If there is, in fact, such a danger, it is heightened by the relative ease in which cadmium oxide is dissolved or leached from a glassy matrix, and this of course is a function of its solubility in the environment of use. Waste water may readily become contaminated from cadmium-soluble glasses in industrial processes. However, a greater danger apparently resides in the ingestion of cadmium-containing glasses in the human system where significant solubility of cadmium oxide, as in stomach acid, could produce a toxic effect.